Linear actuators are utilized for tasks where a linear movement or application of a force is desired. Generally, a linear actuator translates a first element linearly with respect to a second element. Often the second element is fixed with respect to a frame of reference. Linear actuators are utilized in a wide-variety of applications, such as assembly-line processes in which precise linear displacements and reciprocating motions must be generated and maintained. Linear actuators are also utilized in numerous optical systems, such as auto-focus cameras with positioning lenses and laboratory analysis devices, such as interferometers.
An interferometer is an instrument that provides a means of spectral discrimination by way of a precision splitting and recombination of a beam of light. The interferometer achieves this discrimination by varying the pathlength in one half of the beam with respect to the other, and using the resulting interference of the two beams to derive the intensity distribution of wavelengths within the beam.
The mechanism used to vary the pathlength of the variable path portion of the beam must provide repeatable and linear motion in order to preserve the phase and spatial relationship between the two beams as a function of time. The better this mechanism performs, (i.e. the straighter and smoother the motion of the moving mirror), the better the resulting information that can be obtained from the instrument. Thus, an improvement to the efficiency and expense of an interferometer's linear positioning system would be a welcome advance.
Improved linear actuators are advantageous other systems as well, including generally the adjustment, calibration, pointing, focusing and the like, of various technical or scientific instruments including spectrometers and telescopes.
The majority of motion-positioning mechanisms utilized in conventional linear actuators are configured from one of three technologies: ball bearings, roller bearings and dovetails. Such technologies provide advantages such as high load capability, and long travel. They all, however, provide varying degrees of friction and stiction, which are undesirable in systems and devices where precise movement over very short distances is required. The use of ball bearings, roller bearings and/or dovetails, for example, can cause wobble, hysteresis, backlash, and an uncertainty in reproducibility, which can all limit their practical usefulness.
Flexures have also been utilized to implement linear actuators. For examples, flexures have been utilized with auto-focus cameras for the positioning of associated lenses. In general, a flexure is a frictionless, stictionless component that relies upon the elastic deformation (i.e., flexing) of a solid material. Sliding and rolling can thus be eliminated from the design of flexure-based linear actuators. A flexure component or mechanism is generally limited to applications where the required travel is typically no more than 10–15% of the major dimension of the device or system in question. In addition to a lack of internal friction, flexure devices also provide a high stiffness, a high load capacity, and a high resistance to shock. Flexures also exhibit a low sensitivity to vibration. Therefore, because of the frictionless, stictionless nature of a flexure-based positioner, a high degree of vibration can be tolerated. Also, because of the stiffness of a flexure design maintaining a specific position can be greatly enhanced.
The present inventors thus recognize, based on the foregoing, that a need exists for an improved linear actuator for use in devices requiring the precise movement of components and objects. The present inventors have concluded that improvements over conventional and traditional linear actuator devices and methodologies can be achieved through the implementation of an improved flexure-based apparatus and methodologies thereof, as will be further disclosed herein.